The model cannot discover any tools - Codex

Quick fix

Upgrade cc-switch past 3.16.1 and edit cc-switch-model-catalog.json to set supports_search_tool to false for the DeepSeek models.

Symptom

Error outputCopy

在 codex 中要求大模型调用 mcp 工具，大模型无法发现任何工具

English translation

Asking the model to call an mcp tool in codex, the model cannot discover any tools

Cause

In cc-switch 3.16.0 and other early versions, some chat interfaces (deepseek, glm) cannot handle custom MCP tools properly and fail to inject the tool descriptions into the prompt context; this was fixed in 3.16.1. In later versions such as 3.19.2, however, the cc-switch-model-catalog.json config file wrongly sets the supports_search_tool property to true for the deepseek-v4-pro and deepseek-v4-flash models. Codex then assumes the model supports tool_search and loads the MCP tools lazily, but DeepSeek does not actually support that officially, so the tool calls fail.

Fix

1. 1

   Update cc-switch to 3.16.1 or newer to fix the basic MCP injection problem on the chat interface.

2. 2

   Open the cc-switch-model-catalog.json config file, find the deepseek-v4-pro and deepseek-v4-flash models, and change their supports_search_tool property to false.

   // cc-switch-model-catalog.json
   {
     "deepseek-v4-pro": {
       "supports_search_tool": false
     },
     "deepseek-v4-flash": {
       "supports_search_tool": false
     }
   }

Affected Versions

ToolCodex

Version3.16.0 - 3.19.2

PlatformsmacOSWindows

Source Issues

This page is distilled from 2 real issues

• #3463codex 接入 glm ，mcp 不可用
• #6647codex 使用通过 deepseek 预设创建的供应商时，无法使用 mcp 工具

FAQ

I tried using cpa to convert the deepseek chat endpoint into a responses endpoint — why does MCP still not work?

Converting the endpoint alone does not address the root cause. On version 3.16.0 you need to upgrade to 3.16.1; on 3.19.2 you need to change the supports_search_tool setting in cc-switch-model-catalog.json by hand.

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